WLED is a novel solid state lighting source, which is efficient, energy saving and friendly to the environment. Therefore, it is expected to be the fourth-generation lighting source to provide “green lighting”.
Currently commercialized solutions for providing white light by WLED device comprise: “blue LED+yellow phosphor”, “blue LED+yellow+red phosphor” or “blue LED+green+red phosphor”. Although these phosphors provide high luminous efficiency, they have the following deficiencies: (a) poor thermal stability, which causes drift of white light; (b) easy aging of fluorescent paste formed by combination with epoxy resin.
Compared to phosphors, rare earth ions doped luminescent glasses provides many advantages in preparing WLED: (a) easy machining into various shapes and good plasticity; (b) good thermal conductivity and chemical stability; (c) simple processing, readily available materials and low cost; (d) ability to replace epoxy resin. Therefore, rare earth ions doped luminescent glasses provide high application value.
There have been many studies on luminescent glasses, but there are only a few of luminescent glasses which can actually be excited by blue LED chip (440˜480 nm). Chinese patent No. 101830638 A reported a Eu2+ singly doped luminescent glass, which has an optimal excitation wavelength at 349 nm. Chinese patent No. 102701590 A reported a high silica luminescent glass, which has an optimal excitation wavelength extended to be 350˜390 nm. Chinese patent No. 101749642 A reported a luminescent glass excited by blue light, which has an optimal excitation wavelength extended to blue light region (about 440 nm) with the variation in the amount of B2O3. Recently, L.H.C. Andrade reported the excitation and emission spectra of 41.5Al2O3-47.4CaO-7SiO2-2.1MgO-2.0CeO2 (wt. %) (Journal of Alloys and Compounds 510 (2012) 54-59), which has an optimal excitation wavelength at 405 nm. Zijun Liu reported the excitation and emission spectra of 27Al2O3-58CaO-8SiO2-7MgO-xEu2O3 (mol %) (Appl Phys A (2012) 108:777-781), which has an optimal excitation wavelength extended to blue light region (about 440 nm).
In the above mentioned luminescent glasses, some of them have an excitation wavelength which can not be well matched with the emission band of blue LED chip, while the others still have low luminous efficiency. In conclusion, up to now there is no patent or other publications related to the series of luminescent glasses provided by the present invention.